Recently, a rechargeable secondary battery has been widely used as an energy source of a wireless mobile device.
In addition, the secondary battery has been prominent as a power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), and the like, that have been suggested as a scheme for solving air pollution of an existing gasoline vehicle, a diesel vehicle, or the like, using a fossil fuel.
Small-sized mobile devices use one battery cell or several battery cells per one device. In contrast, medium and large-sized devices such as a vehicle, or the like, use a medium and large-sized battery pack in which a plurality of battery cells are electrically interconnected as unit cells, due to necessity of a high output and a large capacity.
Since it is preferable that the medium or large-sized battery packs are manufactured to have a size and a weight as small as possible, they may be stacked at a high degree of integration. In addition, a prismatic battery, a pouch type battery, or the like, having a small weight against a capacity has been mainly used as a battery cell of the medium or large-sized battery pack. Among them, an interest in the pouch type battery having a small weight and a low possibility for leakage of an electrolyte and requiring a low cost at the time of being manufactured has increased.
As unit batteries (battery cell) of the medium or large-sized battery pack, nickel-hydrogen secondary batteries have been mainly used. However, recently, many studies on lithium secondary batteries providing a high output against a capacity, similar to the small battery pack, have been conducted, and some of the lithium secondary batteries have been commercialized.
However, the lithium secondary battery basically has a problem that stability is low. Particularly, the pouch type battery is a leading candidate of a unit battery of the medium or large-sized battery pack due to various advantages as described above. However, the pouch type battery has problems that mechanical rigidity of a battery case is low and an ignitable material such as an electrolyte, or the like, is leaked when a sealing part is separated, such that a risk of a fire is high.
Further, in a lithium polymer battery using a pouch, since electrolytes are injected into cells integrated with each other, when the respective cells are over-charged, a voltage rises and the electrolytes in the cells are decomposed due to overheating, such that inflammable gas is generated in the cells. As a result, a swelling phenomenon that the pouch itself is swelled occurs. In addition, a separator between a cathode and an anode is melted to short-circuit the cathode and the anode, thereby causing a fire. Therefore, stability of the battery may not be secured.
Several studies have been variously and continuously conducted in order to solve these problems. These studies are mainly divided into two methods, that is, a method of chemically preventing over-charge and a method of electrically prevent over-charge, which will be described below in detail.
First, a technology of chemically preventing overcharge using a composition such as a non-aqueous electrolyte, a compound decomposed at the time of the overcharge, or the like, instead of a currently used electrolyte as an electrolyte has been disclosed in Korean Patent Registration No. 0472506, Korean Patent Registration No. 0628629, Korean Patent Laid-Open Publication No. 2006-0121173, and the like.
Second, a technology of electrically preventing overcharge by configuring a circuit blocking an electrical flow or allowing a fuse to be blown (due to overheating) when overheating, an overcurrent, or an overvoltage is generated has been variously disclosed.
As examples, an apparatus of stopping charging by short-circuiting power when a charging voltage becomes a predetermined voltage or more and an apparatus including a voltage sensing heat-generating device generating heat at a predetermined voltage or more and a temperature sensing device sensing the heat generated by the heat-generating device and reversibly turning on/off a current have been disclosed in Korean Patent Laid-Open Publication No. 2007-0010755 (entitled “Apparatus of Stabilizing Secondary Battery”) and Korean Patent Registration No. 0729106 (entitled “Safety Device for Preventing Overcharge and Secondary Battery Having the Same Coupled Thereto”), respectively.
Describing the technologies according to the related art as described above, first, in the case of the method of chemically preventing overcharge, performance is lower as compared with a currently used electrolyte, such that additional development is required. Further, in the case of the method of electrically preventing overcharge, since an independent circuit should be configured and be attached to a battery, the number of electronic components for a configuration is increased, such that it is difficult to manufacture an apparatus and a cost required to manufacture the apparatus is increased. In addition, a design of a circuit is complicated, such that a cost required to design the circuit is increased.
Further, in the case of an apparatus of blocking electricity using overheating, an overcurrent, an overvoltage, or the like, although the number of used components is smaller as compared with the method of providing the independently configured circuit to the battery, the problem as described above may not be completely avoided in that the additional circuit is provided in the battery.
Meanwhile, in order to solve the problems as described above, as shown in FIG. 1, a method in which a battery cell 11 positioned at the outermost portion of a battery module 10 is separated outwardly, such that an electrode tab 12 is broken, thereby blocking power is used. However, in the battery module 10 according to the related art, a terminal 14 and a sensing terminal 14 are positioned at an outer side of the electrode tab 12 positioned at the outermost portion and are not connected to each other to hinder the electrode tab 12 from being broken.